80hp Mariner will not run with a load on it

switch29 · Apr 2, 2012

Hello,

I have a 1983 80hp Mariner that I just got and I finally got it to crank and run in the yard and it will rev up to 5000rpms with no problem and it will go into gear and rev fine but when I put it in the lake and shift it into gear and give it the throttle it dies. Then I have to have the throttle lever all the way down to get it to start back up and then it idles fine again until I try to go then it dies but it will idle around real slow until I hit it WOT then blah it dies. I have cleaned the carbs and replaced all the fuel lines on the carbs and from the tank to the motor. I put new plugs in it. Does anyone know why it will run fine and rev up fine until I try to move the boat with it? Thanks.

CharlieB · Apr 2, 2012

Re: 80hp Mariner will not run with a load on it

The major difference in a motor reving in the yard and the same motor dying once in the water is the amount of exhaust back-pressure of the water column in the leg greatly increases the amount of fuel necessary in the carb idle circuit.

"Best" idle on the hose and 'Best' idle IN gear while IN the water are a big difference. You also need even more idle mixture fuel to provide enough for the motor to accelerate once you open the throttle. The total difference is near a quarter turn richer in the water then it is running on the hose at home.

switch29 · Apr 2, 2012

Re: 80hp Mariner will not run with a load on it

CharlieB said:
The major difference in a motor reving in the yard and the same motor dying once in the water is the amount of exhaust back-pressure of the water column in the leg greatly increases the amount of fuel necessary in the carb idle circuit.

"Best" idle on the hose and 'Best' idle IN gear while IN the water are a big difference. You also need even more idle mixture fuel to provide enough for the motor to accelerate once you open the throttle. The total difference is near a quarter turn richer in the water then it is running on the hose at home.

Thanks for the info, so what do you suggest? Should I adjust the air mixture srews or something like that? I am going to pick up a fuel pump rebuild kit tomorrow.

carholme · Apr 2, 2012

Re: 80hp Mariner will not run with a load on it

And more importantly, never do this:

"run in the yard and it will rev up to 5000rpms with no problem and it will go into gear and rev fine"

or one of these days, you may be picking up bits and pieces of your motor from all over the neighbourhood. if not bits and pieces of yourself or your loved ones!

Gerry

switch29 · Apr 2, 2012

Re: 80hp Mariner will not run with a load on it

carholme said:
And more importantly, never do this:

"run in the yard and it will rev up to 5000rpms with no problem and it will go into gear and rev fine"

or one of these days, you may be picking up bits and pieces of your motor from all over the neighbourhood. if not bits and pieces of yourself or your loved ones!

Gerry

I no about the over reving and the motor coming apart. I did not rev it to 5k in gear in the yard I did that in neutral in the lake. It wont get to 1200 rpms with it in gear and thats the problem I am trying to get info about.

carholme · Apr 2, 2012

Re: 80hp Mariner will not run with a load on it

Sorry about that, I was just going by what you wrote:

"I have a 1983 80hp Mariner that I just got and I finally got it to crank and run in the yard and it will rev up to 5000rpms with no problem and it will go into gear and rev fine but when I put it in the lake and shift it into gear and give it the throttle it dies."

Gerry

switch29 · Apr 2, 2012

Re: 80hp Mariner will not run with a load on it

So does anyone have any suggestions that might point me in the right direction? Before I start randomly swapping parts.

1nebel0 · Apr 3, 2012

Re: 80hp Mariner will not run with a load on it

Charlie gave it to you..yes you adjust the mixture screws...and Gerry was just trying to help given what you wrote...

Bondo · Apr 3, 2012

Re: 80hp Mariner will not run with a load on it

switch29 said:
So does anyone have any suggestions that might point me in the right direction? Before I start randomly swapping parts.

Ayuh,.... Figure out WHY it's goin' Lean....

switch29 · Apr 3, 2012

Re: 80hp Mariner will not run with a load on it

Ok thanks. I am going to take it to the water this afternoon and once I get it running I will take my screw driver and back out the screws you are talking about. I have always been told not to adjust those but after an engine is a certain age then its alright? I hate to mess it up and not be able to get it back to the factory settings. I thought about taking the carbs apart again so I can remove the jet screws this time and make sure they dont have a blockage on the back side of them. Also could one of you tell me which carb is the high speed carb? Is it the top or bottom carb because since I can get it to idle around but not speed up it seem that I may need to be focusing on the high speed carb first correct? Thanks!

CharlieB · Apr 3, 2012

Re: 80hp Mariner will not run with a load on it

Carbs MUST BE clean before adjusting. Dirt and mineral accumulation over time restrict fuel flow, the small passages for the idle are the first to show signs such as poor acceleration or won't idle IN gear and IN the water, yet will rev freely, seeming like nothing is wrong, when actually the carbs need serious attention, cleaning.

Both carbs open and close exactly the same. It is critical the linkage be adjusted with the carbs fully closed so the smallest movement of the linkage moves BOTH throttle plates the same. There is no 'low speed' or 'high speed' carb, each carb MUST BE adjusted very nearly identically so that each cyl fed by each carb will run the same.

switch29 · Apr 3, 2012

Re: 80hp Mariner will not run with a load on it

Now thats great information! I will take them off again today and remove the screws to make sure there is zero restriction and I will put a new diaphram kit in the fuel pump and run it down to the river to see what I got. Thanks CharlieB!

switch29 · Apr 3, 2012

Re: 80hp Mariner will not run with a load on it

Oh and I did fail to mention that I had to adjust the idle way out to get it idle in the first place so with that being said, it makes since that something is clogged because by me adjusting the idle way out and then trying to run it in gear would throw everything way off. Hmm what a dumb newbie mistake. I hope thats the case anyway.

switch29 · Apr 3, 2012

Re: 80hp Mariner will not run with a load on it

switch29 said:
Oh and I did fail to mention that I had to adjust the idle way out to get it idle in the first place so with that being said, it makes since that something is clogged because by me adjusting the idle way out and then trying to run it in gear would throw everything way off. Hmm what a dumb newbie mistake. I hope thats the case anyway.

Well to my surprise I think I found the problem. There is no fire to the bottom two cylinders at all. So do ya think that would cause it to shut off when I try to go?

CharlieB · Apr 5, 2012

Re: 80hp Mariner will not run with a load on it

CDIElectronics has a great Ignition Troubleshooting Guide available for FREE download on their Support pages, get it, follow the easy to read detailed instructions on how to test and troubleshoot your ignition to positively determine exactly what is at fault.

Remember, there is NO RETURN on electrical parts, test twice to PROVE any fault before ordering or changing any parts.

You will need a DVA meter or a DVA adaptor for a Volt/Ohm meter. A DVA adaptor can be built easily and cheaply following the instructions posted here
http://forums.iboats.com/showthread.php?t=374544

80hp Mariner will not run with a load on it

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